The AIDS pandemic and associated generation of multiple antibiotic resistance among pathogens like M. tuberculosis, and recalcitrant endemic diseases such as malaria, all indicate innovative approaches to vaccine development are needed. Towards this goal, we are developing an innovative approach to antigen delivery, amenable to the display of HIV-1 and HIV-2 clad virus proteins via a novel, particulate virus-like organelle termed the gas vesicle, which is naturally used for flotation of aquatic prokaryotes. We have studied the gas vesicle of salt-loving halophilic archaebacteria extensively, both genetically and biochemically, and found that these uniquely stable protein structures are encoded by a cluster of genes, including two, gvp A and gvp C, that encode major structural proteins. The vesicles have inherent adjuvant activity. Thus, in the absence of exogenous adjuvant, TNP-crosslinked to the vesicle surface, as well as a peptide expressed on the vesicle through gvp C genetic engineering, each elicited an immune response, with memory, from immunized mice. We have incorporated unique restriction sites into gvp C, identified an insertion site in this gene that tolerates up to 705 bp inserts, expressed SIV sequences from this site and demonstrated both presentation to the immune system and immunologic memory for the expressed sequences. During the period of this proposal, we plan to (1) construct SIV-GV recombinants to constitute a multiepitope display library of all SIVsm genes, (2) express and accumulate SIV-GV library members and evaluate their display of inserted antigen sequences, (3) evaluate library member functions in terms of response polarization- in vivo, and in vitro in terms of altered cytokine/chemokine mRNA levels in tissues and macrophages and in terms of eliciting specific immune responses and (4) prepare a gas vesicle based multiepitope library displaying the entire HIV genome. Initial use of SIV will permit subsequent in vivo assessment of the SIV epitope library, testing of epitope presentation and delivery in a primate model. By applying our expertise in molecular genetics and protective epitope identification, the proposed research will provide the groundwork for establishing the feasibility of using this submicroscopic particle as a multiepitope display vehicle. Using the same molecular genetic based strategy, this unique system can then be applied to the development of an HIV/SHIV vaccine that will provide the uniquely flexible large-scale production of a safe, singularly inexpensive, and stable vaccine.